Close #146

Temporary workaround for https://github.com/Homebrew/homebrew/issues/39669

Close #233

setopt extendedglob on zsh caused caret in grep pattern to be expanded.
Problem identified and patch submitted by @lazywei.

[zsh] `head -n1` instead of `head -1`

at least my version of head wants -n1 to only display the first line

No error on ~INVALID_USERNAME**<TAB>

fix typo in README.md

Close #228

/cc @alerque

- Ask for user confirmation before running `install --bin`
- Removed `s:fzf_rb` since `install --bin` will create a wrapper
  executable that just runs Ruby version on the platforms where prebuilt
  binaries are not available.

Support for vi insert mode in upcoming fish 2.2.0

This fixes the issue where "inline-info" is not immediately rendered
when the terminal is resized.

Code submitted by @lydell

Close #214